1. Field of the Invention
The present invention relates to a lamp reflector, particularly a lamp reflector suitable for a head lamp, a fog lamp, or the like, mounted on a two-wheel or four-wheel vehicle, or the like; and a lamp reflector manufacturing method. More particularly, the present invention relates to a lamp reflector which has a substrate high in surface smoothness due to the material composition of a substrate constituting the lamp reflector, and also relates to a method for manufacturing such a lamp reflector.
2. Description of the Related Art
Currently, thermoplastic resin, for example, polyphenylene sulfide resin (PPS resin) is used as a basic material (base resin) of a substrate constituting a lamp reflector for use in a head lamp or a fog lamp for a vehicle. A reinforcement material such as whiskers, calcium carbonate powder, or the like, is kneaded and dispersed into the basic material in order to enhance the rigidity and increase the molding dimensional stability and the heat resistance.
Specifically, wollastonite (calcium silicate whiskers) or heavy calcium carbonate occurring in nature is used as the whiskers or the calcium carbonate powder. Such a substance is crushed and classified into powder with desired grain size, and the thusly obtained powder is kneaded into the basic material.
FIG. 9 schematically shows a partial section of a related-art lamp reflector 100.
The surface of a substrate 101 made of the aforementioned material composition exhibits a rough surface with irregularities. The surface of a metal coating 102 of aluminum or the like, which is provided on the upper surface of the substrate 101, is affected by the irregularities of the surface of the substrate 101. Thus, the surface of the metal coating 102 has irregularities.
The aforementioned related art has the following technical problems.
First, natural wollastonite (calcium silicate whiskers) and heavy calcium carbonate used as reinforcement material differxe2x80x94in their constituent components and granular shape of the powder obtained by crushingxe2x80x94in accordance with a mine where they were mined. In addition, the granular shape of the power also varies in accordance with the particular crushing method used.
Accordingly, when resin obtained by kneading such a natural reinforcement material is subjected to injection molding, the melting viscosity is not constant; that is, the melting viscosity varies. Therefore, it becomes difficult to ensure the smoothness of the substrate surface, or it becomes difficult to ensure dimensional accuracy. To prevent such difficulties, there was a disadvantageous technique wherein the temperature of a mold or the conditions of injection molding always had to be controlled in accordance with the properties of the resin.
In addition, when a thick top coat 103 is formed as a protective film on the related-art lamp reflector 100, the film thickness of the top coat 103 becomes larger in concave portions 103a of the metal coating 102 while the film thickness becomes smaller in convex portions 103b of the metal coating 102. Accordingly, there occurs a difference in optical refractive index between the concave portion 103a and the convex portion 103b. As a result, there arose a problem that fog generated in the concave portions 103a had a bad influence on the light distribution performance.
It is therefore an object of the present invention to provide a lamp reflector in which reinforcement materials to be kneaded and dispersed into a basic material forming a substrate of the lamp reflector are specified so that the particle shape and the granularity (particle size) distribution of the reinforcement materials are made uniform enough to fix the viscosity of resin in which the reinforcement materials have been kneaded and dispersed. Thus, the lamp reflector has a substrate in which desired surface smoothness and rigidity are ensured, while the dimensional accuracy is high (because the substrate is a molded product). It is also an object of the present invention to provide a method of manufacturing such a lamp reflector.
In order to attain the foregoing and other objects, the present invention includes the following aspects.
In a lamp reflector according to a first aspect of the present invention, the reflector is provided with a substrate made of a composition containing at least polyphenylene sulfide resin (PPS resin), synthetic calcium carbonate whiskers, and synthetic calcium carbonate (CaCO3).
In this aspect, natural substances having uneven properties are not used. Instead, fibrous synthetic calcium carbonate whiskers and granular synthetic calcium carbonate (CaCo3)xe2x80x94having even, consistent, propertiesxe2x80x94are used as reinforcement materials to be kneaded into polyphenylene sulfide resin (hereinafter referred to as xe2x80x9cPPS resinxe2x80x9d) adopted as a basic material of the substrate forming the lamp reflector.
Thus, the surface smoothness and the rigidity are made compatible. That is, the viscosity of the resin in which the reinforcement materials have been kneaded and dispersed is made constant, so that a substratexe2x80x94of a lamp reflector, which substrate is a molded productxe2x80x94having a high dimensional accuracy can be obtained.
In addition, there is eliminated such a problem that the temperature of a mold, or the conditions of injection molding always must be adjusted in accordance with the properties of the resin in which the reinforcement materials have been kneaded and dispersed. Thus, the productivity is improved.
In a lamp reflector according to a second aspect of the invention, the composition of the substrate constituting the lamp reflector is compounded and adjusted so that the PPS resin of the first aspect is in a range of from 30 weight % to 50 weight %, the synthetic calcium carbonate whiskers of the first aspect are in a range of from 5 weight % to 40 weight %, and the synthetic calcium carbonate of the first aspect is in a range of from 20 weight % to 60 weight %.
In this second aspect, the surface smoothness and the rigidity of the substrate can be made compatible more surely, and workability by injection molding is also enhanced.
Specifically, if the content of PPS resin is much, the surface smoothness of the substrate will be ensured easily, but the rigidity and the heat resistance will deteriorate. On the contrary, if the content of synthetic calcium carbonate whiskers or synthetic calcium carbonate is too much, the rigidity will be ensured, but the surface smoothness will deteriorate. In addition, because PPS resin is reduced relatively, the flowability of molding resin will be lowered so that injection molding will be difficult. However, in the aforementioned second aspect of the invention, each of the requirements for the surface smoothness, the rigidity of the substrate, and the molding ease is satisfied.
Incidentally, injection molding is one of the typical techniques in a resin molding method. According to this technique, molten resin material is put into a metal mold under pressure, and is then solidified and molded by cooling if it is a thermoplastic resin or by heating if it is a thermosetting resin.
In a lamp reflector according to a third aspect of the invention, the substrate contains the synthetic calcium carbonate according to either the first or the second aspects, and also has an average particle size not larger than 2 xcexcm.
In this third aspect, the granular shape of synthetic calcium carbonate is maintained not larger than a constant size. Thus, the surface smoothness of the molded substrate is ensured more reliably.
In a lamp reflector according to a fourth aspect of the invention, a reflecting mirror surface made of a metal coating is formed directly on a surface of the substrate according to any one of the first to third aspects and a protective film (top coat) for preventing metal degradation is formed on a surface of the reflecting mirror surface.
In this fourth aspect, a reflective metal coating of aluminum or the like can be formed directly on the substrate surface to form a reflecting mirror surface. Accordingly, it is not necessary to provide an under coat layer which may have a bad influence on the heat resistance of the metal coating surface. Thus, the heat resistance is enhanced.
In addition, because it is not necessary to provide an under coat layer, a process of treating an organic solvent contained in the under coat waste liquor can be eliminated, thereby avoiding unsanitary environmental problems. Further, a process of solidifying the under coat is eliminated, so that the process is simplified and productivity is improved.
In a lamp reflector according to a fifth aspect of the invention, the lamp reflector is divided into a plurality of surfaces by divisional boundary portions, wherein a step is formed in each divisional boundary portion. With a configuration, injection molding is easily performed. Further, a desired plane smoothness and a desired rigidity are ensured.
Also, in a stepped reflecting mirror which is designed to control the light distribution only by using the plurality of surfaces on the reflecting mirror, an under coat layer is eliminated by the configuration of the fourth aspect. As a result, there is no irregular reflection due to the under coat layer, as there is in the related art wherein the under coat layer is gathered in step portions, which has been problematic hitherto. Thus, it is possible to obtain an excellent light distribution.
In a lamp reflector according to a sixth aspect of the invention, a lamp reflector defined in any one of the first to fifth aspects is obtained by injection molding using high pressure gas.
In this sixth aspect, injection molding with high-pressure gas can be performed under the condition wherein the properties of the resin materialxe2x80x94which is prepared for the injection molding and in which reinforcement materials have been kneaded and dispersedxe2x80x94are stabilized. Thus, the substrate can be molded with a high dimensional accuracy.
Accordingly, the lamp reflector of present invention contributes a technically significant improvement in the quality performance of the lamp reflector which is disposed in a head lamp, a fog lamp, or the like, mounted on a two-wheel or four-wheel car, or the like. Further, the method of manufacturing the lamp reflector according to the present invention improves productivity in the process for manufacturing the lamp reflector.